Paclitaxel On Human Anaplastic Thyroid Cancer Cells In Vitro Experimental Study

Objectives:1. To investigate the proliferative effect of paclitaxel against humananaplastic thyroid carcinoma cells (DRO).2. To study the change of cell cycle and apoptosis after paclitaxel onDRO cells.3. To investigate the expression of VEGF mRNA, bcl-2 mRNA and baxmRNA stimulated by paclitaxel on DRO cells and to explore the possiblemolecular mechanism of therapy of paclitaxel on human anaplasticthyroid carcinoma.Methods:1. DRO cells were cultured in RPMI1640 containing 10% fetal bovineserum, 1×10⁵U/L penicillin-streptomycin, 0.1 mmol/L MEM-nonessentialamino acid and 1 mmol/L pyruvic acid sodium.2. DRO cells were treated by paclitaxel with different concentrations andfor varied length of acting time. Cell proliferation was measured bymethyl thiazolyl tetrazolium (MTT) assay.Survival ratio (%)=experimental group OD/control group OD×100%Inhibition ratio (%)=(1-survival ratio)×100%IC₅₀ was calculated after 72h of incubation with paclitaxel.3. The cell cycle and apoptosis were studied by flow cytometry while6.25μg/L paclitaxel was exposed to DRO cells at 24h,48h and 72h respectively.4. The expression of VEGF mRNA, bcl-2 mRNA and bax mRNA incells were detected by RT-PCR after 48h of incubation with 6.25μg/Lpaclitaxel.Results:1. Paclitaxel had marked suppressive effect on the growth of DRO cellsin vitro. The percentage of viable cells decreased in a time-dependentand dose-dependent manner for DRO cells. IC₅₀ value was 10μg/L after72 h of incubation with paclitaxel.2. Paclitaxel could block cell cycle at G₂/M phase and induce apoptosis.After 48h of incubation with 6.25μg/L paclitaxel, there mostly appearedthe induction of apoptosis, the apoptosis rate was 32.76%±1.54%.3. VEGF mRNA was down regulated by paclitaxel. The expression ofbcl-2 mRNA was not changed, while that of bax mRNA was up regulatedafter paclitaxel treatment.Conclusions:1. Paclitaxel significantly inhibits the proliferation of DRO cells.2. Paclitaxel arrests the cell cycle at the G₂/M phase and induces theapoptosis. It suggests that paclitaxel is a choice of chemotherapeutic drugfor human anaplastic thyroid carcinoma.3. Paclitaxel significantly decreases the expression of VEGF mRNA inDRO cells. bcl-2 may not be related to the apoptosis induced by paclitaxel in DRO cells. The up-regulated expression of bax might playan important role in paclitaxel-induced apoptosis.